Revati is the twenty-seventh and last, ruled by Mercury, its symbol a fish (also a drum), its deity Pūṣan — protector of travellers, guide of roads, finder of lost cattle, the one who conducts souls where they're going. The name means 'abundant'.
Mechanically Mercury is mind and conveyance; Pūṣan is the guide. Together: delivery. This is the last of the twenty-seven, and the last one's work isn't ending, it's handing people on to the next stretch. The fish guiding in the water is exact — it doesn't come ashore itself, it brings the lost ashore. So the tradition links this segment to compassion, to completed journeys, to transition; and it's the softest of the twenty-seven, because whoever escorts people can't be hard.
Where you'll recognise it: gentleness with people, often a transitional figure in others' lives (they pass through you and go on), feeling for animals and for the small, a sense of completion mixed with wistfulness, and real difficulty knowing where you yourself should stop. Running well, you're the best guide: bringing people to the right place, making transitions less painful, giving a gentle ending. Stuck, you give until you're hollow — everyone delivered and you still in the water, or unable to let people go because you can't bear it. After this one comes Ashwini again: the round of twenty-seven closes, the Moon returns to the start, and someone else's first step begins here.